Rail flaw detector mechanism



April 9, 1935.

H. c. DRAKE Er AL RAIL FLAW DETECTOR MECHANISM Filed April 22, 1932 W X R mm m 9. A

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Patented Apr. 9, 1935 UNITED STATES BAIL FLAW DETECTOR MECHANISM Harcourt C. Drake, Hempstead, and George L. Jones, Garden City, N; Y., assignors to Sperry Products, Inc., Brooklyn, N. Y. a corporation or New York Application April 22,1932, Serlal No. 606,808

8 Claims.

This invention relates to rail flaw detector mechanisms of the type employed in the Sperry rail flaw detector car. In said mechanism, the current is generated within the car and supplied to sets of brushes which lead the current into and out of the rail to establish an electromagnetic field surrounding the rail. Sets of induction coils are then moved along the rail through the electromagnetic field cutting the lines of force to gen-- erate an E. M. F. The coils arearranged in opposite pairs so that when both coils are cutting the same number of lines of force no differential E. M. F. is generated but when a region of flaw is encountered, the vcoils being arranged in tandem, one coil will cut a different number of lines of force from the other coil to generate a differential E. M. F. The current brushes are carried by a current brush carriage suspended from the car body and the induction coils are carried by a decarriage. In the forms of detector mechanism which are here illustrated, the coils are carried in metallic casings which engage the rail. The current brush carriage and the detector carriage are also of metal, which are therefore electrical conductors.

Because of the construction described above, it has been found that in some instances false indications as of a flaw were obtained where no flaw existed, and this was traced to the fact that since the current brush carriage, detector carriage, and the casings for the induction coils were all of conductive material, electric circuits and condenser eflects were established in these various parts because they engaged the rail through which current was passing. Such circuits and condensers were, of course, of variable characteristics, and the variations in flux thus set up by these factors were picked up by the induction coils in the same manner as a flaw.

It is the principal object of our invention, there-- fore, to make provision in the flaw detector system hereinbetore described for preventing setting up such stray electric circuits and the establishment of condansersZwhose variable characteristics may possibly induce flux in the induction coils.

Further objects and advantages of our invention will become apparent in the following detailed description thereof.

In the accompanying drawing,

Fig. 1 is a side elevation of a portion or a Sperry rail flaw detector car showing one form of our invention applied thereto.

Flgi 2 is an enlarged view of the search unit shownin the Fig. 1 tom 01 the invention.

tector carriage suspended from the current brush Fig. 3 is a section taken on the line 3-3 of of Fig. 2. r

Fig. 4 is a side elevation of a modified form or detector unit having our invention applied thereto.

Fig. 5 is a plan view, partly sectioned, of a detail of one of the induction coil mountings of Fig. 4 showing our invention applied thereto.

Referring to Fig. 1 of the drawing, there is disclosed a portion of a Sperry rail flaw "detector 10 car I0 from which is suspended the detector 7 mechanism by means of pistons II and retracting cables I2. The pistons operate in fluid pressure cylinders l3 whereby the detector mechanism may be lowered against the action of the 15 retracting mechanism. Current is supplied to the rail from a generator within the car-body to sets 01 current brushes l5 and I6 carried by a current brush carriage H. The said sets of brushes are in engagement with the rail and lead current into and out of the same to establish an electromagnetic field surrounding the rail. The current brush carriage travels along the rail on any suitable means, such as wheels I. Flaws are detected by means of a search unit which is supported on a detector carriage 2| which isinturn supported on the current brush carriage II. The detector carriage 2| may ride upon the rails on means such as wheels 22. In the form of search unit shown, the induction coils are mounted within cylinders 23, said cylinders being of metal adapted to ride upon the rail. The axes of the coils are equidistant from the rail so that as the car travels along the rail the'coils cut an equal number of lines or force. Since the coils are connected in opposition no E. M. F. is generated until a region or flaw is encountered which displaces the electromagnetic field so that on enteringsaid field one coil cuts more or less lines of force than the other to induce an E. M. F.

Referring to Fig. 2, it will be seen that the metallic casings 23 enclosing the induction coils are mounted in the frame 20' which is supported on the detector carriage 2| by metallic bolts 25. The detector carriage 2| is itself of conductive material and is supported on the currentbrush carriage by means such as metallic bolts 26. The current brush carriage I1 is likewise of conductive material. It will now be seen that since current of large amperage is flowing through the rail, it the frame 2|! were also of conductive material there would be ready opportunity for the establishment or local electric circuits from the rail through the casings 23 and thus by various paths through casing 2| to wheels 22 or through casing 2i and easing II to wheels i8 and back to the rail, since all of said parts are of conductive material. Since the casings 23 are of metallic material and the coils are formed by wires which are encased in insulation, condensers.

are established with the covering of the wires forming the insulation between two conductors. It is further apparent that these local circuits and this condenser effect is not constant but would vary with many factors, and such variations would cause a changing flux which would affect the induction coils 'to generate an E. M. F. which would give a false indication as of a flaw.

We obviate this condition and prevent the establishment of such local electric circuits and condenser eflfects by the following means: The frame 20 in which the casings 23 are mounted and by which the coils are supported on the detector carriage, and hence on the current brush carriage, is formed ofan insulating material such as Bakelite which efiectively' prevents the establishment of any of the local electric circuits mentioned above, as will be seen from Fig. 3, because any such circuit extending from the casings 23 is effectively interrupted by the insulating frame 20. Similarly, the condenser effect within the casings is prevented since there is no outlet for the discharge of such condenser, the coils not being grounded since they are supported in the insulating frame 20'. Fln'ther prevention of the establishment of local electric circuits and condenser effects is obtained by insulating the brushes l5 and i6 and the lower portion ll of the carriage H which supports said brushes from the upper portion ll" of said carriage by means of insulation l8.

The principle disclosed above for eliminating flaws due to the establishment of local circuits and condenser effects may be applied, also to another form of Sperry detector unit. In this form of detector unit each coil 24 is mounted within a casing 23' which is individually supported for movement within the detector carriage 2i"upon a frame 33 pivoted in said carriage at 3|. The details of this mounting are disclosed in Fig. 5 wherein it is seen that the frame 30 is fixed to a stub shaft 3| journalled in the side walls 32 of the detector carriage. Each casing 23' is pressed into engagement with the rail by means such as a hairpin spring 33 surrounding the shaft 3| .and anchored at one end against a fixed bolt 36 in the walls 32 of the detector carriage and pressing with its other end upon the arm 30. The detector carriage is supported from the current brush carriage by means such as bolts 26 and springs 40, said carriagebeing in engagement with the rail by means such as rollers 42.

It has been seen that the same condition exists in theFig. 4 form of the invention as in the Fig. 1 form, namely, that unless provision were made to prevent the establishment of local electric circuits and condenser 'efl'ects suchcircuits could be established through casings 23', arms 30, shafts 3|, walls 32, wheels 42 and the rail.

while condenser effects could be established within the casing 23' between the casing and the coil 24, the wrapping around the coils acting as a di-electric. We, therefore, make provisiorrfor preventing the establishment of such local circuits and condenser effects sothat the variations in these factors will not be able to generate E. M. F35 within thecoils. For this purpose we prevent the establishment of local circuits by providing Bakelite bearings 50' between the shafts 3! (which carry arms 38) and the casings 23' on the onehand, and the walls 32 of the detector carriage on the other. Said insulating bearings 50 are provided with flanges 5! to complete the insulation between the hubs 52 of arms 30 and the side walls 32 of the carriage.

There is still another path through which such circuits may be established, said path being by way of arms 30, or springs 35, and the fixed bolt 36. Therefore, we provide insulating bearings such as Bakelite bearings 55 between the fixed bolt 36 and the side walls 32 of the detector carriage.

For preventing the establishment of condenser effects within the casing 23' we have shown the end wall 21 of the said casing as being formed of insulating material, such as Bakelite. The coil 24 is supported out of contact with the walls of casing 23' by means of insulating brackets 28 fixed to the end wall 21. By this construction there is no path by which the condenser may discharge.

. In accordance with the provisions of the patcut statutes, we have herein described the principle and operation of our invention, together with the apparatus which we now consider to represent the best embodiment thereof, but we desire to have it understoodthat the apparatus shown is only illustrative and that the invention can be carried out by, other means. Also, while it is designed to use the various features and elements in the combination and relations described, some of these may be altered and others omitted without interfering with the more gen-- eral results outlined, and to such use.-

Having described our invention, what we claim and desire to secureby Letters Patent is:

1. In a flaw detector mechanism for rails and the like, said mechanism being adapted to move along the rails, in combination, a source of current, means for supplying said current to the rail including a current brush carriage, said carriage comprising a frame having wheels engaging the rail and sets of current brushes for leading current into and out of the rail, means supported by said carriage and responsive to variations in flux around the rail for detecting flaws therein, and means for insulating from said wheels and brushes the portion of said carriage frame which supports said responsive means.

2. In a flaw detector mechanism for rails and the like, said mechanism being adapted to move along the rails, in combination, a source of current, means for supplying said current to the rail, means responsive to variations in flux around the rail for detecting flaws therein, said last-named means comprising an induction coil, a conductive casing therefore adapted to engage the rail, a support for said casing on said carriage, and means for insulating said casing from said carriage.

the invention extends 3. In a flaw detector mechanism for rails and the like, said mechanism being adapted to move rail,

along the rails, in combination, a source or current, means for supplying said current to the rail, means responsive to variations in flux around the rail for detectin last-named means comprising a plurality o! induction coils, a conductive casing for each/o! said coils, means whereby said carriage supports said casings, and means whereby said casings are insulated from said carriage.

5. In a flaw detector mechanism for rails and the like, said mechanism being adapted to move along the rails, in combination, a source of current, means for supplying said current to the means responsive to variations in flux around the rail for detecting flaws therein, said last-named means comprising a plurality oi induction coils, a conductive casing for each of said coils, means whereby said carriage supports said casings, means whereby said casings are insulated from said carriage, and means whereby said carriage 'is insulated from the rail.

6. In a flaw detector mechanism for rails and the like, said mechanism being, adapted to move along the rails, in combination. a source of current, means for supplying said current to the rail, means responsive to variations in flux around the rail for detecting flaws therein, said last-named means comprising an induction coil,

bearings for supporting said casing for pivotal movement in said carriage.

flaws therein. said a conductive casing 7. In a'flaw detector mechanism for rails and the like, said mechanism being adapted to move along the rails, in combination, a source of current, means for supplying said current to the rail, means responsive to variations in flux around the rail for detecting flaws therein, said last-named means comprising an induction coil, a conductive casing therefore adapted to engage the rail, means including an arm pivoted in said carriage and connected to said casing for supporting said casing in said carriage, and means for insulating said arm irom said carriage.

8. In a flaw detector mechanism for rails and the like, said mechanism being adapted to move along the rails in combination, a source or current, means for supplying said current to the rail, means responsive to variations in flux around the rail for detecting flaws therein, said last-named means comprising an induction coil,

therefore adapted to engage the rail, means including an arm in said carriage and connected to said casing for supporting said casing in said carriage, means'ior insulating said arm from said carriage, spring means between .said carriage and said am (or pressing said easing into engagement with the rail, and means for insulating said spring means from said carriage.

HARCOURT C. DRAKE. GEORGE L. JONES.

pivoted 

